This invention relates to a dyalyzer using hollow fibers, in which a dialysate can flow uniformly through a space between any adjacent hollow fibers and which can be effectively worked when used as an artifical kidney.
Such a dialyzer as illustrated in FIG. 1 is known. The known dialyzer comprises a bundle of about 10,000 hollow fibers 1 made of a semi-permeable material such as regenerated cellulose. The fibers 1 have an inner diameter of 200 to 300 microns and are arranged densely in a cylindrical housing 2 made of a synthetic resin and having both ends open. The fibers 1 are secured to the housing 2 in a liquid-tight fashion by a high molecular adhesive agent 3 such as polyurethane resin. The hollow fibers 1 are made to communicate at one end with a solution inlet port 4 and at the other end with a solution outlet port 5. The peripheral wall of the housing 2 is provided with a dialysate inlet port 6 and a dialysate outlet port 7 near the respective ends of the housing 2. Through the dialysate inlet port 6 a dialysate is introduced into the housing 2 to flow through the exterior of the hollow fibers 1. Through the dialysate outlet port 7 the dialysate is discharged from the housing 2. To elevate the dialysis efficiency, a dialyzer of this type is installed in a substantially vertical position, and the solution, e.g. blood, and the dialysate are made to flow downwards and upwards, respectively.
In the above-described dialyzer, however, the dialysate flows only along particular portions of the hollow fibers 1, not uniformly along the entire fibers 1, as indicated by arrows in FIG. 1. This undesirable phenomenon is called "channeling". If channeling takes place, some portions of the fibers 1 indicated by "A" in FIG. 1 do not work for dialysis. That is, the dialysate comes into a good contact with those portions of the fibers 1 which are near dialysate ports 6 and 7, and as for the other portions of the fibers 1 it tends to flow where it meets less resistance. Further, the dialysate cannot come into a good contact with the innermost fibers, though it may be sufficiently contacted with the outermost fibers.
In order to avoid channeling, a dialyzer with a so-called "overflow mechanism" has been invented. The overflow mechanism is constituted by two annular ribs which support the hollow fibers in the vicinity of the dialysate inlet port and the dialysate outlet port, respectively. In this type of a dialyzer, the dialysate outlet port is provided below the upper edge of the annular rib, so that the dialysate is sucked up and uniformly flows over the edge of the rib and discharged through the dialysate outlet port. As a result, the dialysate can flow all along at least outermost ones of the hollow fibers. Indeed the overflow mechanism helps enhance the dialysis efficiency to some degree, but it fails to improve the dialysis efficiency at the innermost hollow fibers.